$2.)$ A test bottle containing just seeded $($dilution water has its DO level drop by $0\mathrm{.}8m\frac{g}{L}$ in a $5-$day test. A $300$mLBOD bottle filled with $30mL$ of wastewater and the rest with seeded dilution water experiences a drop of $7\mathrm{.}3m\frac{g}{L}$ in the same period $(5$ days$).$ Calculate the BOD$5$ of the wastewater.